How to Quickly Discover VoIP Snags

Video Transcript

Hi, my name is Mike Danseglio. And today I’m going to be talking to you a little bit about how to troubleshoot VoIP performance issues. Connection issues, performance issues, things like delayed speech, or dropped connections, or garbled voice communications could be really annoying. There are some really basic ways to actually start to troubleshoot the problem to start to indentify and encapsulate where the issues are so that you can move on to resolving the issues. Some of the tools are really basic so you can just get an idea of what’s going on. However, there are some more advanced tools that give you more performance information and more depth as to what’s going on and I’ll mention those towards the end of this presentation.

So first part is I’d like to assume that we are opening a communication, a VoIP channel to akami.net. The first thing I’m going to do is ping it, you’ve all seen ping before. Certainly ping is a really useful, effective tool for determining whether our systems here can reach their systems there, whether your network or host can actually reach that. You can see that I can actually been able to reach that from my host here. That’s great. That’s a good first set. However, there are a couple of other things here that we want to try just to make sure we are not having any trouble reaching akami.net. We’re going the throw the -a command into it. What that does is actually help resolve the name, in case akami.net was not resolving, or resolving to a different host you would be able to see some difference. Right now it is resolving at a pretty consistent fashion. However, depending on the time of day, akami.net actually does DNS round-robin. So I will see different hosts resolving for akami.net. That’s an interesting potential VoIP issue, because every single time it resolves to a different IP address it may resolve to something with a different performance threshold. The results may get better or worse depending on what it resolves to.

The second tool I’d like to show you is something that some people know and some don’t. It’s called tracert (traceroute). And what it is is an extension of ping, but what it does is use a crafty thing in ping. It uses the TTL, the Time To Live portion, of ping to actually end-of-life these and return the packet as unreachable at every step in the routing of this packet. What you actually wind up seeing is a list of hosts between this client that I’m on now and akami.net, wherever it’s resolving to.

You can see here we are resolving the name to deploy.akamitechnologies.com. That’s useful to know that we actually got a name. Interestingly we can see between hops seven and eight and between hops nine and ten, that there is a significant amount of delay in the packet routing. This is usually where you start to see VoIP issues degrade. Now, the difference from 8 milliseconds to 100 milliseconds is not such a great difference, but the difference between 100 milliseconds and 500 milliseconds might be significant.

So, that’s the kind of thing you want to look for when you actually take this type of traceroute. When you see the trace route come up, you generally want to look for the big hops. The difference between seven and eight and between eight and nine, those are the big delay factors so then you want to try to instantiate a VoIP connection with something on the close side of seven and then on the far side of hop seven to see if that’s the delay. If the delay introduced in that hop is actually causing the VoIP issues. Then, you can determine that it is between sea1.alter.net and sea1.gblx.net. That’s getting closer and closer to honing in on the problem so you can identify it and resolve it.

One other thing I want to show you that ping does that people don’t know, is ping -t. Ping-t just keeps pinging all day long. While this may seem annoying it’s an interesting way to get an average over time, round trip time, between this host and the target host. There are a lot of automated tools that do this in a bunch of better ways. If I were you looking at performance issues around VoIP, look at other solutions, alternate solutions that automate some of this so you do not have to sit here at a command prompt and watch ping round-trip times all day long. That can get really boring and frankly it is not going to yield a whole lot of interesting data that you can prove with. Thanks for watching today.